一Oracle 日志的特性总结
1 oracle 日志切换规律（从最大sequence#号切换到最小sequence#号）
eg 如下所示：下个当前日志组会是sequence#号为27的5号日志组
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 NO 32 CURRENT
2 YES 28 INACTIVE
3 YES 29 INACTIVE
4 YES 30 INACTIVE
5 YES 27 INACTIVE
6 YES 31 INACTIVE
6 rows selected.
SQL> alter system switch logfile ;
System altered.
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 YES 32 ACTIVE
2 YES 28 INACTIVE
3 YES 29 INACTIVE
4 YES 30 INACTIVE
5 NO 33 CURRENT
6 YES 31 INACTIVE
6 rows selected.
Oracle 重做联机日志文件
Oracle联机日志恢复案例
联机日志文件过小引发的log file 相关等待
Oracle联机日志文件丢失或损坏的处理方法
联机日志损坏时的恢复（正常关闭数据库）
2 快速转换oracle日志组状态active为inactive
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 YES 32 INACTIVE
2 YES 34 INACTIVE
3 YES 35 INACTIVE
4 NO 36 CURRENT
5 YES 33 INACTIVE
6 YES 31 INACTIVE
SQL> alter system switch logfile;
System altered.
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 YES 32 INACTIVE
2 YES 34 INACTIVE
3 YES 35 INACTIVE
4 YES 36 ACTIVE
5 YES 33 INACTIVE
6 NO 37 CURRENT
6 rows selected.
查询数据文件头部scn情况如下：
SQL> select hxfil,fhscn from x$kcvfh;
HXFIL FHSCN
---------- ----------------
1 2781239221
2 2781239221
3 2781239221
4 2781239221
5 2781239221
6 2781239221
7 2781239221
8 2781239221
11 2781239221
12 2781239221
13 2781239221
SQL> select sequence#,first_change#,next_change# from v$log_history;
SEQUENCE# FIRST_CHANGE# NEXT_CHANGE#
---------- ------------- ------------
32 2781218249 2781218300
33 2781218300 2781219174
34 2781219174 2781219184
35 2781219184 2781239220
36 2781239220 2781239424
SQL> alter system checkpoint;
System altered.
SQL> select hxfil,fhscn from x$kcvfh;
HXFIL FHSCN
---------- ----------------
1 2781239456
2 2781239456
3 2781239456
4 2781239456
5 2781239456
6 2781239456
7 2781239456
8 2781239456
11 2781239456
12 2781239456
13 2781239456
11 rows selected.
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 YES 32 INACTIVE
2 YES 34 INACTIVE
3 YES 35 INACTIVE
4 YES 36 INACTIVE
5 YES 33 INACTIVE
6 NO 37 CURRENT
3 clear 日志组的执行条件
eg：
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 NO 38 CURRENT
2 YES 34 INACTIVE
3 YES 35 INACTIVE
4 YES 36 INACTIVE
5 YES 33 INACTIVE
6 YES 37 ACTIVE
SQL> alter database clear logfile group 6;
alter database clear logfile group 6
*
ERROR at line 1:
ORA-01624: log 6 needed for crash recovery of instance CRM (thread 1)
ORA-00312: online log 6 thread 1: '/oracle/CRM2/CRM/redo06.log'
ORA-00312: online log 6 thread 1: '/oracle/CRM2/CRM/redo06b.log'